Experimental cross section study of ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$: Searching for new neutron-deficient Pa isotopes

The fusion-evaporation reaction ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ aimed at synthesizing new neutron-deficient protactinium isotopes has been studied at the gas-filled recoil separators SHANS and SHANS2. The cross sections for the $xn$ and $pxn$ evaporation channels were measured. The calculation by the statistical model HIVAP was performed to reproduce the experimental data. The quasifission process in the ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ reaction was also studied with time-dependent Hartree-Fock theory and the improved quantum molecular dynamics model. It is shown that the influence of quasifission in the analysis of evaporation residue cross sections of this reaction can be neglected.

Figure 1

Energy spectrum for $\alpha$ particles following the implanted residues within a time window of 2 s measured in the ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ reaction at a beam energy of 228 MeV.

Figure 2

Two-dimensional scatter plot of parent and daughter $\alpha$-particle energies for correlated ER-$\alpha 1\text{−}\alpha 2$ events measured in the ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ reaction at a beam energy of 228 MeV. The searching time windows were 50 ms for the ER-$\alpha 1$ pair and 2 s for the $\alpha 1\text{−}\alpha 2$ pair.

Figure 3

Time evolution of the mass density in the tip and side orientations for head-on collisions of ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ at an incident energy of $E_{\mathrm{c}.\mathrm{m}.}=164.8$ MeV.

Figure 4

Cross sections for the fusion-evaporation reaction ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$: (a) $xn$ channels, (b) $pxn$ channels. Experimental data measured in the present work are shown by the symbols. The values calculated using HIVAP (${\mathrm{C}}_f=0.70$) are shown by dashed lines. Bass barrier $E_{\mathrm{bass}}^{*}$ is calculated according to Ref. [26].